1. Field of the Invention
The present invention relates to a silver halide photographic material. More particularly, it is concerned with a silver halide photographic material used in a photomechanical process.
2. Description of the Prior Art
In the field of graphic arts, image-forming systems which can ensure ultra-hard photographic characteristics (especially a gamma value of at least 10) are required for the purpose of satisfactory reproduction of continuous-tone images or line images in halftone images.
As for the method for obtaining high contrasty photographic characteristics by the use of a stable developer, there are known methods of respectively using the hydrazine derivatives disclosed (in a developer or a photographic material), e.g., in U.S. Pat. Nos. 4,224,401, 4,168,977, 4,166,742, 4,311,781, 4,272,606 and 4,211,857. According to these methods, ultra-hard and high-speed photographic characteristics can be achieved and, what is more, as it is allowable to add a sulfite in a high concentration to a developer, the stability to aerial oxidation of a developing agent in the developer is improved to a great extent, compared with that in a lith developer.
On the other hand, means for reducing changes in pH of a developer by aerial oxidation and processing of photosensitive materials are disclosed in JP-A-62-186259 and JP-A-60-93433 (the term "JP-A" as used herein means an "unexamined published Japanese patent application).
However, it has be revealed that success only in suppressing the conversion of a developing agent and the change in pH of a developer cannot lead to steady achievement of satisfactory photographic characteristics.
As a result of analyzing the cause of the aforesaid troubles, we have found that variation of the sulfite concentration also has an influence upon photographic characteristics. Since the influence of a variation of the sulfite concentration upon photographic characteristics is small in conventional ordinary development-processing systems, exclusive of lith development, it is beyond expectation that the variation of the sulfite concentration has a considerable influence in hard-tone enhanced systems utilizing nucleation with hydrazine derivatives.
In a lith development system, a sulfite can be used in an only slight amount. Therefore, the lith developer is designed so as to contain a sulfite in the form of an aldehyde adduct (including formaldehyde adduct), thereby minimizing the variation of a sulfite concentration. In the hard gradation system utilizing hydrazine nucleation, on the other hand, the developer used contains a sulfite in a high concentration. In such a system, the attempt to keep the sulfite concentration to be constant using the same -means as adopted in the lith development system is attended by various disadvantages.
Therefore, it is desired to use hydrazine nucleation compounds which is hard to undergo the influence of variation of the sulfite concentration.
Hydrazine derivatives having various structures have been used as nucleator.
There are disclosed the compounds represented by RNHNHCHO in JP-B-58-9410 (the term "JP-B" as used herein means an "examined Japanese patent publication), JP-B-58-30568 and U.S. Pat. No. 4,650,746, the compounds represented by (R.sup.1)(R.sup.2)NCON(R.sup.3)-X-NHNHCHO in JP-B-59-52820, the compounds represented by (R.sup.1)(R.sup.2)NCON(R.sup.3)-X-NHNHCOR.sup.4 in JP-B-1-15855, and the compounds represented by R.sup.1 NHCON(R.sup.2)CO-(CH.sub.2).sub.n -Ar-NHNH-V-R.sup.5 in JP-A-1-105943 (wherein R, R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 respectively represent a monovalent substituent, Ar represents an arylene group, the former X represents a bivalent aromatic group residue, the latter X represents a phenylene group, V represents --SO.sub.2 -- or --CO--, and n represents an integer of from 1 to 10). In those references, it is disclosed that R, R.sup.1 and R.sup.2 each may contain a ballast group and a group capable of accelerating the adsorption of the compound onto silver halide grains which have been conventionally used in couplers. R.sup.4 and R.sup.5 each represents a hydrogen atom, an aliphatic group or an aromatic group, with specific examples including methyl and phenyl groups.
In addition, there are disclosed in JP-A-60-140340 the hydrazine derivatives represented by formula R.sup.1 -NHNH-G-R.sup.2 wherein R.sup.1 represents a substituted or unsubstituted aryl group, R.sup.2 represents a hydrogen atom, or a substituted or unsubstituted alkyl, aryl or aryloxy group, and G represents --CO--, a sulfonyl group, a sulfoxy group, a phosphoryl group or an imino group. Therein, it is also described that in a preferred case R.sup.1 may contain a ballast group or a group capable of accelerating the absorption onto silver halide grains.
Further, the compounds represented by Ar-NHNH-COR, wherein Ar contains a nondiffusible group (the same as a ballast group) or a group capable of adsorbing onto silver halide grains and R is a substituted alkyl group, are disclosed in JP-A-2-37.
The compounds represented by (R.sup.1)(R.sup.2)NCON(R.sup.3)-(A.sub.2 -L).sub.m -Ar-NHNH-Z (wherein R.sup.1 and R.sup.2 each represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heterocyclic group or an amino group, R.sup.3 represents a hydrogen atom or an alkyl group, A.sub.r and A.sub.2 each represents an aryl group, or a heterocyclic group, L represents a linking group, Z represents a formyl group, an acyl group, a sulfonyl group, a carbamoyl group, a sulfamoyl group, an alkoxycarbonyl group, or a thioacyl group), wherein at least either R.sup.1 or R.sup.2 is an amino group, are disclosed in JP-A-2-947.
In U.S. Pat. Nos. 4,925,832 and 4,798,780 are disclosed the intramolecularly cyclized hydrazine compounds.
In U.S. Pat. No. 4,937,160 and European Patent 444,506 are disclosed the hydrazine compounds containing a pyridinium group.
Specific examples of the compounds disclosed in prior arts are illustrated below. ##STR2##
However, some of these known hydrazine compounds cannot exhibit sufficient nucleation activity, while others cannot fulfil the new requirement for sulfite concentration independency although they have high nucleation activity.